Regulation of Y-organ function and ovarian development by the TGF-β signaling pathway in the swimming crab (Portunus trituberculatus).

Portunus trituberculatus is an economically important marine crab in China, and the mature ovaries of females possess high nutritional and market value. The Y-organ (YO) is an important endocrine gland in crustaceans that primarily synthesizes ecdysteroids and other steroid hormones. Although its functional status influences ovarian development, the underlying regulatory mechanisms remain poorly understood. This study elucidates how the TGF-β signaling pathway regulates YO function and ovarian development in this species. Unmated and mated females were treated with FK506 (pathway activator) and SB431542 (pathway inhibitor), respectively. Transcriptome sequencing, RT-qPCR, ELISA, and histological analysis were employed to investigate the effects of TGF-β signaling on YO gene expression, 20-hydroxyecdysone (20E) synthesis, and ovarian development. Transcriptomic analysis identified 345 and 788 differentially expressed genes in the YO following pathway activation and inhibition, respectively. TGF-β activation down-regulated Pt-spo and Pt-dib, up-regulated Pt-sad, and decreased hemolymph 20E levels, whereas inhibition produced opposite effects, indicating a negative regulatory role in 20E synthesis. The pathway also modulated expression of juvenile hormone esterase, follistatin, and neuro-immune-related genes (Pt-npal, Pt-gpcr, Pt-gst and Pt-tle). Histologically, pathway activation promoted oocyte development from oogonia to vitellogenic stages, while inhibition delayed ovarian maturation. The TGF-β signaling pathway can affect neuroendocrine processes and species metabolism in the YO, thereby indirectly regulating ovarian development.